1. Field of the Invention
The present invention relates generally to laser scanning systems, and more particularly to an automatic bar code symbol reading system in which an automatic hand-supportable laser scanner can be interchangeably utilized as either a portable hand-held laser scanner in an automatic "hands-on" mode of operation, or as a stationary laser projection scanner in an automatic "hands-free" mode of operation.
2. Brief Description of the Prior Art
Bar code symbols have become widely used in many commercial environments such as, for example, point-of-sale (POS) stations in retail stores and supermarkets, inventory and document tracking, and diverse data control applications. To meet the growing demands of this recent technological innovation, bar code symbol readers of various types have been developed for scanning and decoding bar code symbol patterns and producing symbol character data for use as input in automated data processing systems.
In general, prior art hand-held bar code symbol readers using laser scanning mechanisms can be classified into two major categories.
The first category of hand-held laser-based bar code symbol readers includes manually-actuated trigger-operated systems having lightweight, hand-held laser scanners which can be supported in the hand of the user. The user positions the hand-held laser scanner at a specified distance from the object bearing the bar code symbol, manually activates the scanner to initiate reading and then moves the scanner over other objects bearing bar code symbols to be read. Prior art bar code symbol readers illustrative of this first category are disclosed in U.S. Pat. Nos. 4,387,297 to Swartz; U.S. Pat. No. 4,575,625 to Knowles; U.S. Pat. No. 4,845,349 to Cherry; U.S. Pat. No. 4,825,057 to Swartz, et al.; U.S. Pat. No. 4,903,848 to Knowles; U.S. Pat. No. 5,107,100 to Shepard, et al.; U.S. Pat. No. 5,080,456 to Katz, et al.; and U.S. Pat. No. 5,047,617 to Shepard, et al.
The second category of hand-held laser-based bar code symbol readers includes automatically actuated systems having lightweight triggerless hand-held laser scanners which can be supported in the hand of the user. The user positions the hand-held laser scanner, at a specified distance from the object bearing the bar code the presence of the object is automatically detected, the presence of the bar code symbol on the object is detected, and thereafter the detected bar code symbol automatically read. Prior art illustrative of this second category of laser-based bar code symbol reading systems are disclosed in U.S. Pat. No. 4,639,606 to Boles, et al., and U.S. Pat. No. 4,933,538 to Heiman, et al.
While prior art hand-held and stationary laser scanners have played an important role in the development of the bar code symbol industry, these devices have, however, suffered from a number of shortcomings and drawbacks. For example, hand-held laser scanners, although portable and lightweight, are not always convenient to use in assembly-line applications where the user processes bar coded objects over an extended period of time, or where the user requires the use of both hands in order to manipulate the objects. In some applications, hand-held laser scanners are difficult to manipulate while simultaneously moving objects or performing other tasks at a point-of-sale terminal. Stationary laser scanners, on the other hand, provide a desired degree of flexibility in many applications by allowing the user to manipulate bar coded objects with both hands. However, by their nature, stationary laser scanners render scanning large, heavy objects a difficult task as such objects must be manually moved into or through the laser scan field.
Attempting to eliminate the problems associated with the use of hand-held and stationary laser scanners, U.S. Pat. No. 4,766,297 to McMillan discloses a bar code symbol scanning system which combines the advantages of hand-held and stationary fixed laser scanners into a single scanning system which can be used in either a hands-on or hands-free mode of operation.
The bar code symbol scanning system in U.S. Pat. No. 4,766,297 includes a portable hand-held laser scanning device for generating, electrical signals descriptive of a scanned bar code symbol. In the hands-on mode of operation, a trigger on the hand-held laserl scanning device is manually actuated each time a bar code symbol on an object is to be read. The system further includes a fixturel having a head portion for receiving and supporting the hand-held laser scanning device, and a base portion above which the head portion is supported at a predetermined distance. In the hands-free mode of operation, the hand-held laser scanning device is supported by the fixture head portion above the fixture base portion in order to allow objects bearing bar code symbols to pass between the head and base portions of the fixture. In order to detect the presence of an object between the head and base portions of the fixture, the fixture also includes an object sensor operably connected to the hand-held laser scanning device. When the object sensor senses an object between the head portion and the base portion, the object sensor automatically initiates the hand-held laser scanning device supported in the fixture to read the bar code symbol on the detected object.
While the bar code symbol scanning system of U.S. Pat. No. 4,776,297 permits reading of printed bar code information using either a portable "hands-on" or stationary "hands-free" mode of operation, this system suffers from several significant shortcomings and drawbacks as well.
In particular, in the hands-on mode of operation, scanning bar code symbols requires manually actuating a trigger each time a bar code symbol is to be read. In the hands-free mode of operation, scanning bar code symbols requires passing the object bearing the bar code between the head and base portions of the fixture. However, in many instances where both hands are required to manipulate a bar coded object, the object is too large to be passed between the head and base portions of the fixture and thus scanning of the bar code symbol is not possible.
In an attempt to address such problems, several hand-held projection laser scanners have been developed for omnidirectional code symbol scanning. Examples of such systems include the NCR 7890 presentation scanner from the NCR Corporation and the LS9100 omnidirectional laser scanner from Symbol Technologies, inc. While each of these systems produces an omnidirectional laser scan pattern from a hand-supportable housing and have hands-free and hands-on modes of operation, each of these scanning devices suffer from a number of shortcomings and drawbacks. In particular, the spatial extent of the laser scan pattern produced from each of these scanners frequently results in the inadvertent scanning of code symbols on products placed near the scanner during its hands-free mode of operation. In the hands-on mode of operation, it is virtually impossible to use the scanners to read bar code symbol menus provided in diverse application environments. Moreover, in each of these scanner designs, the scanner is tethered to its base unit by a power/signal cord, and the user is required to handle the scanner housing in an awkward manner in the hands-on mode of operation, resulting in strain and fatigue and thus a decrease in productivity. In addition, the control structure provided in each of these hand-held projection scanners operates the scanner components in a manner which involves inefficient consumption of electrical power, and prevents diverse modes of automatic code symbol reading which would be desired in portable scanning environments.
Thus, there is a great need in the bar code symbol reading art for a bar code symbol reading system which overcomes the above described shortcomings and drawbacks of prior art devices and techniques, while providing greater versatility in its use.